Separation and identification of Group IIIA cations

May contain Fe(OH)3 and Mn02. H20. Wash with a little hot water. 

Dissolve a small portion of the ppt. in 1 ml of 1 1 HN03 with the aid (if necessary) of 3-4 drops of 3 % H202 solution or 1 drop of saturated H2S03 solution. Boil (to decompose H202), cool thoroughly, add 0-05-0-1 g sodium bismuthate, shake, and allow the solid to settle. 

Dissolve another portion of the ppt. in dilute HC1 (filter, if necessary). 

The original solution or substance should be tested with K4[Fe(CN)6] and with KSCN to determine whether Fe2+ or Fe3+ (5). 

Blue upper layer (containing chromium pentoxide it does not keep well). 

---

The precipitation of Group IIIA cations with ammonia solution is carried out according to the procedure given in Table V12. The separation and identification of Group IIIA cations in the presence of some less common ions, as described in Table VII.6 commences with the precipitate obtained with ammonia. 

Table 6.5 Separation and identification of Group IIIA cations in the presence of Ti, Zr, Ce, Th, U,...

---